1. Technical Field
This invention relates generally to internal combustion engines, and more particularly to pistons therefor.
2. Related Art
Engine manufacturers are encountering increasing demands to improve engine efficiencies and performance, including, but not limited to, improving fuel economy, reducing oil consumption, improving fuel systems, increasing compression loads and operating temperatures within the cylinder bores, reducing heat loss through the piston, improving lubrication of component parts, decreasing engine weight and making engines more compact, while at the same time decreasing the costs associated with manufacture.
While desirable to increase the compression load and operation temperature within the combustion chamber, it remains necessary to maintain the temperature of the piston within workable limits. Accordingly, although desirable to increase the compression load and operation temperature within the combustion chamber, achieving this goal comes with a tradeoff in that these desirable “increases” limit the degree to which the piston compression height, and thus, overall piston size and mass can be decreased. This is particularly troublesome with typical piston constructions having a closed or partially closed cooling gallery to reduce the operating temperature of the piston. The cost to manufacture pistons having upper and lower parts joined together along a bond joint to form the closed or partially closed cooling gallery is generally increased due to the joining process used to bond the upper and lower parts together. Further, the degree to which the engine weight can be reduced is impacted by the need to make the aforementioned “cooling gallery-containing” pistons from steel so they can withstand the increase in mechanical and thermal loads imposed on the piston.